/**
 * http://mongodb.github.io/node-mongodb-native
 * http://mongodb.github.io/node-mongodb-native/3.0/api/
 */
//DB库
var MongoDB = require('mongodb');
var MongoClient = MongoDB.MongoClient;
const ObjectID = MongoDB.ObjectID;

var Config = require('./config.js');

class Db {
    static getInstance() { /*1、单例  多次实例化实例不共享的问题*/
        if (!Db.instance) {
            Db.instance = new Db();
        }
        return Db.instance;
    }

    constructor() {
        this.dbClient = ''; /*属性 放db对象*/
        this.connect(); /*实例化的时候就连接数据库*/
    }

    connect() { /*连接数据库*/
        let _that = this;
        return new Promise((resolve, reject) => {
            if (!_that.dbClient) { /*1、解决数据库多次连接的问题*/
                MongoClient.connect(Config.dbUrl, (err, client) => {
                    if (err) {
                        reject(err)
                    } else {
                        _that.dbClient = client.db(Config.dbName);
                        resolve(_that.dbClient)
                    }
                })
            } else {
                resolve(_that.dbClient);
            }
        })
    }

    find(collectionName, json) {
        return new Promise((resolve, reject) => {
            this.connect().then((db) => {
                var result = db.collection(collectionName).find(json);
                result.toArray(function(err, docs) {
                    if (err) {
                        reject(err);
                        return;
                    }
                    resolve(docs);
                })
            })
        })
    }
    update(collectionName, json1, json2) {
        return new Promise((resolve, reject) => {
            this.connect().then((db) => {
                //db.user.update({},{$set:{}})
                db.collection(collectionName).updateOne(json1, {
                    $set: json2
                }, (err, result) => {
                    if (err) {
                        reject(err);
                    } else {
                        resolve(result);
                    }
                })
            })
        })
    }
    insert(collectionName, json) {
        return new Promise((resolve, reject) => {
            this.connect().then((db) => {
                db.collection(collectionName).insertOne(json, function(err, result) {
                    if (err) {
                        reject(err);
                    } else {
                        resolve(result);
                    }
                })
            })
        })
    }
    remove(collectionName, json) {
        return new Promise((resolve, reject) => {
            this.connect().then((db) => {
                db.collection(collectionName).removeOne(json, function(err, result) {
                    if (err) {
                        reject(err);
                    } else {
                        resolve(result);
                    }
                })
            })
        })
    }
    getObjectId(id) { /*mongodb里面查询 _id 把字符串转换成对象*/
        return new ObjectID(id);
    }
}
module.exports = Db.getInstance();

// 数据库的测试
/*
var myDb = Db.getInstance();

setInterval(function() {
    console.time('start');
    myDb.find('user', {}).then(function(data) {
        // console.log(data);
        console.timeEnd('start');
    })

}, 1000)

setTimeout(function() {
    console.time('start1');
    myDb.find('user', {}).then(function(data) {
        //console.log(data);
        console.timeEnd('start1');
    })

}, 3000)

var myDb2 = Db.getInstance();

setTimeout(function() {
    console.time('start3');
    myDb2.find('user', {}).then(function(data) {
        //console.log(data);
        console.timeEnd('start3');
    })

}, 5000)

setTimeout(function() {
    console.time('start4');
    myDb2.find('user', {}).then(function(data) {
        //console.log(data);
        console.timeEnd('start4');
    })

}, 7000)*/